var envents = require("events");
var Emitter = events.EmitterEmitter;
function Radio(radioNum){
    Emitter.call(this);//实现对Emitter继承
    this.radioNum = radioNum;
}
Radio.prototype = Emitter.protootype;//实现对Emitter继承
Radio.prototype.start = function(){
    console.log(this.radioNum+ "started");
}
Radio.prototype.stop = function(){
    console.log(this.radioNum+ "stopped");
}
module.exports = Radio;//对外公布Dog构造函数 